In recent years, metabolic diseases including diabetes are on rapid increase as life has become richer in eating habits. Intake of excessive nutrients induces secretion of a larger amount of insulin to cause indirectly a collapse of metabolic balance, thus leading to a reduction of glucose tolerating function (hyperglycemia), diabetes, hyperlipemia, arteriosclerosis, etc. Especially in diabetic patents, the insulin function is insufficient and the glucose tolerance is lowered, so that blood glucose level is remarkably increased after meals to cause complications such as damages in blood capillary and arteriosclerosis.
For the prophylaxis and treatment of such diseases are effective foods or materials which can hardly induce an increase in blood glucose level or are capable of inhibiting a secretion of a large amount of insulin after uptake of necessary nutrition. Therefore, there is continuing need for a material capable of inhibiting the hydrolysis of the ingested starch into glucose and a material capable of saving an insulin secretion.
From the above aspects, various studies have been made on an amylase inhibitor being capable of inhibiting an activity of an amylase which hydrolyzes starch into glucose. Amylase inhibitors were reported to be contained in wheat. Since then, the amylase inhibitors of wheat origin have been investigated.
U.S. Pat. No. 3,950,319 discloses that the amylase inhibitor extracted from wheat with water, an acid or an aqueous alcohol is used for the treatment of diabetes, obesity and the like.
The prior amylase inhibitor of wheat origin does not achieve the effect as expected when orally administered. Further, it has the disadvantage of high cost and reduced inhibition of digestion to glucose, particularly for the digestion of heat cooked starch such as cooked rice.